1. Field of the Invention
The present invention relates to a golf club head, and especially to a hollow metal club head.
2. Description of the Related Art
In general, a hollow metal head for a golf club is composed of four parts, i.e., a crown, a face, a sole and a hosel.
FIG. 6 is a partial sectional view illustrating a conventional hollow metal head. The metal head P1 is composed of a crown C2, a face (not shown), a sole S2 and a hosel H2. The hosel H2 has a shaft insertion hole 10, which extends obliquely upward so as to open. The bottom wall 11 closes the lower end of the shaft insertion hole 10. Accordingly, in the metal head P1, the inside 13 of the hosel H2 and a space 12 defined by the crown C2, the face (not shown) and the sole S2 are separated from each other by means of the above-mentioned bottom wall 11. The front-end portion of a shaft 9 for a golf club is inserted into the shaft insertion hole 10 of the hosel H2 and fixed thereto. The conventional metal head P1 described above will hereinafter be referred to as the "prior art 1".
FIG. 7 is a partial sectional view illustrating another conventional hollow metal head. The metal head P2 is composed of a crown C3, a face (not shown), a sole S3 and a hosel H3. The hosel H3 has a shaft insertion hole 14, which extends obliquely upward so as to open. A bottom wall 15 having a through-hole 15a is formed at the lower end of the shaft insertion hole 14. Accordingly, in the metal head P2, the inside 17 of the hosel H3 and a space 16 defined by the crown C3, the face (not shown) and the sole S3 communicate with each other through the through-hole 15a of the bottom wall 15. The front-end portion of a shaft 9 for a golf club is inserted into the shaft insertion hole 14 of the hosel H3 and fixed thereto. The conventional metal head P2 described above will hereinafter be referred to as the "prior art 2".
Irregularity in weight of golf club heads usually occurs when manufacturing them. However, in any one of the prior arts 1 and 2, it is impossible to compensate the above-mentioned irregularity and in addition, to change uniformly the position of the center of gravity of the head. The front end of the shaft 9 comes into contact with the bottom wall 11, 15 of the hosel H2, H3 and is fixed thereto in such a condition by means of a fastening means such as an adhesive. It is therefore impossible to adjust the mounting position of the shaft 9 relative to the hosel H2, H3.
In the prior art 1, the inside 13 of the hosel H2 and the space 12 defined by the crown C2, the face (not shown) and the sole S2 are separated from each other by means of the bottom wall 11. Such a construction causes the following problems. More specifically, with respect to manufacture of the golf club head, when there are applied, for example, a step of forming the crown C2, the face (not shown) and the hosel H2 as an integral body and a subsequent step of welding the sole S2 to the above-mentioned integral body, there is a possibility that a part of a weld bead may separate in a molten state from the weld bead during forming it and solidifies so as to form a metallic piece, which is freely movable within the above-mentioned space 12. The space 12 is insulated from the outside, with the result that the inside of the head cannot be cleaned and the above-mentioned metallic piece cannot be discharged outside. The existence of the metallic piece remaining in the inside of the head causes the occurrence of the noise when using the golf club head.
On the contrary, in the prior art 2, the bottom wall 15 of the hosel H3 has the through-hole 15a formed thereon, with the result that the inside of head can be cleaned through the through-hole 15a and the above-mentioned metallic piece can be removed. However, a shoulder portion is formed on the periphery of the through-hole 15a, which locates at the side of the hosel H3, so as to project perpendicularly to the inner surface of the hosel H3. Accordingly, it is not easy to insert a flexible tube for cleaning the inside of the head into the through-hole 15a, leading to a complicated cleaning operation. In addition, an adhesive for fixing the shaft 9 to the hosel H3 may pass through the above-mentioned through-hole 15a into the inside of the head and solidify to form a lump of the adhesive. The thus formed lump of the adhesive causes the occurrence of the noise when using the golf club head. A grip mounted on the rear end of the shaft 9 has an air hole formed on its bottom wall portion. There may be caused a problem that water coming into the shaft 9 through the air hole infiltrates into the head through the through-hole 14.